Shake table tests of a prefabricated ultra-thin shell specimen

Abstract

The seismic performance of a prefabricated ultra-thin triangular shell dome structure developed in the scope of the Prefabricated Ultra-Thin Concrete Shells project was investigated through shake table tests. Shell dome structures are usually designed to withstand vertical loads, but in seismic-prone regions, they also must sustain horizontal seismic forces. Following the architectural and engineering design presented in the companion papers, a set of experimental tests were carried out on the LNEC 3D seismic table with a 1:3 reduced-scale model of the developed prototype produced by the prefabrication company SPRAL. An extensive testing protocol was carried out during which horizontal seismic actions were imposed in two orthogonal directions. The reference seismic action, generated from the regulatory spectra in NP EN 1998-1:2010, was scaled by several multiplicative factors from 25% to 400% and applied sequentially. The specimen was instrumented with accelerometers at various points to estimate the inertia forces generated and displacement transducers at the joints between prefabricated elements to record any relative movements. Dynamic properties (frequencies, mode shapes, and damping coefficients) were tracked during the testing sequence to detect eventual degradation due to the seismic tests. The combination of the various results with the observations made during the tests made it possible to evaluate the seismic performance of the specimen. The seismic tests demonstrated that the thin shell dome structure was able to sustain horizontal seismic loads above the seismic design level.